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# duplexify
Turn a writeable and readable stream into a single streams2 duplex stream.
Similar to [duplexer2](https://github.com/deoxxa/duplexer2) except it supports both streams2 and streams1 as input
and it allows you to set the readable and writable part asynchronously using `setReadable(stream)` and `setWritable(stream)`
```
npm install duplexify
```
[](http://travis-ci.org/mafintosh/duplexify)
## Usage
Use `duplexify(writable, readable, streamOptions)` (or `duplexify.obj(writable, readable)` to create an object stream)
``` js
var duplexify = require('duplexify')
// turn writableStream and readableStream into a single duplex stream
var dup = duplexify(writableStream, readableStream)
dup.write('hello world') // will write to writableStream
dup.on('data', function(data) {
// will read from readableStream
})
```
You can also set the readable and writable parts asynchronously
``` js
var dup = duplexify()
dup.write('hello world') // write will buffer until the writable
// part has been set
// wait a bit ...
dup.setReadable(readableStream)
// maybe wait some more?
dup.setWritable(writableStream)
```
If you call `setReadable` or `setWritable` multiple times it will unregister the previous readable/writable stream.
To disable the readable or writable part call `setReadable` or `setWritable` with `null`.
If the readable or writable streams emits an error or close it will destroy both streams and bubble up the event.
You can also explicitly destroy the streams by calling `dup.destroy()`. The `destroy` method optionally takes an
error object as argument, in which case the error is emitted as part of the `error` event.
``` js
dup.on('error', function(err) {
console.log('readable or writable emitted an error - close will follow')
})
dup.on('close', function() {
console.log('the duplex stream is destroyed')
})
dup.destroy() // calls destroy on the readable and writable part (if present)
```
## HTTP request example
Turn a node core http request into a duplex stream is as easy as
``` js
var duplexify = require('duplexify')
var http = require('http')
var request = function(opts) {
var req = http.request(opts)
var dup = duplexify(req)
req.on('response', function(res) {
dup.setReadable(res)
})
return dup
}
var req = request({
method: 'GET',
host: 'www.google.com',
port: 80
})
req.end()
req.pipe(process.stdout)
```
## License
MIT
## Related
`duplexify` is part of the [mississippi stream utility collection](https://github.com/maxogden/mississippi) which includes more useful stream modules similar to this one.
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